text: it("Should return 0 for input '' ", function() {
      expect(Calculator('')).toEqual(0);
  });
  it("Should return 3 for input 3 ", function() {
      expect(Calculator('3')).toEqual(3);
  });
  it("Should return 8 for input 3,5 ", function() {
      expect(Calculator('3,5')).toEqual(8);
  });
  it("Should return 13 for input 5,8 ", function() {
      expect(Calculator('5,8')).toEqual(13);
  });
  